1. Field of the Invention
The invention relates to a method of reforming gasolines under low pressure in the presence of at least one catalyst in a reaction zone, one part of which at least is heat controlled by a heat exchange device disposed therewithin the heat exchange device having hollow plates.
2. Description of the Prior Art
The quality of gasolines, and particularly their octane number, can be improved by reforming at about 500.degree. C., in the presence of hydrogen, within several solid catalytic beds containing precious metals, such as platinum, activated by different additives such as rhenium and iridium, for example (patents U.S. Pat. No. 4,588,495, FR-B-2,593,824, FR-B-2,597,496, FR-B-2,600,668).
The reaction for reforming gasolines is generally an endothermic reaction and a drop in the reaction temperature usually takes place as the transformations progress.
The traditional method for reforming gasolines comprises three, and generally four, adiabatic reactors, disposed in series and connected together by two, and generally three, heating ovens whose role is to heat the reagents and to bring their temperature thus into the desired reaction temperature range.
The application of anti-pollution standards leads to a reduction of the lead concentration in gasolines and will in the long run lead to suppressing organo-plumbic additives in motor car fuels for controlled ignition engines. These regulations impose on refiners an increase in the severity of the operating conditions for reforming units so as to satisfy the criteria of quality required for satisfactory operation of motor car engines: Thus, refiners are led to reducing more and more the operating pressure of these reforming units. In fact, if the severity of the operating conditions is increased, in particular the octane number of the reformed products, the yield drops and the only means of offsetting this drop in yield is to operate at a lower pressure.
But, such low pressure operation is expensive and R. G. McClung et al. have shown that the limitation is due to the pressure losses through the equipment, the optimum of these losses being situated at about 0.35 to 0.5 MPa (Hydrocarbon Processing, Sept. 1983, pages 80-84).
It thus seems difficult to carry out reforming at pressures less than 0.7 MPa, and even less than 1 MPa.